Failure of a control valve in an industrial process almost always impacts plant operation. Generally, control valve failures may impact the response of the control valve to control signals. In particular, a control valve may become less-responsive or sluggish to a control signal, which may lead to degradation in control performance that induces process variability, which is costly to the plant operators or worse, may lead to hazardous conditions. Thus, early detection of control valve degradation or deterioration may allow for orderly scheduled maintenance of a control valve in a manner that would prevent disruption of operation to a process plant.
Control valve performance degradation may occur for a number of reasons. Generally, deterioration of component parts may be a primary factor. Deterioration of parts, however, is typically detected only upon degradation of control valve operation to the point where the control valve malfunctions, due to, for example, a component failure, at which point it may be too late to perform preventative maintenance. One approach to preventative maintenance may be to physically inspect the components of a control valve on a periodic basis. This option, however, is costly as it requires that the process control loop using the control valve be shut down and/or that the control valve be removed and disassembled for review.